
Public Blockchain: is an open network which allows everyone to join and make transactions as well as participate in the consensus process. The best-known public blockchain consists of Bitcoin and Ethereum with open source and smart contract blockchain platforms. For example, Ethereum [1]} is a distributed public blockchain network similar to most platforms such as Bitcoin. A big advantage of Ethereum is its capability of automatic digital asset management through smart contracts which run on Ethereum virtual machine. Blocks are verified and appended to the blockchain by a PoW algorithm managed by miners to achieve a secure, tamper-resistant consensus among all nodes in the network. Each block needs a certain amount of gas, a currency in Ethereum, to be consumed as part of its execution, and pays for miners as the reward of mining the block.

Private Blockchain: is an invitation-only network managed by an authority and all activities such as transaction writing and retrieval in the blockchain need to be permissioned by a validation mechanism. While the private blockchain approach assumes that the network is operated by a single entity, consortium blockchains operates under the management of a group of owners. They restrict user access to the network and the transactions performed by the network members. Due to the ability to provide collaborative control in the network, consortium blockchains enable interconnected business transformation among organizations and innovative business models.

Consortium Blockchain: is a blockchain platform governed by multiple organizations instead of only a single organization. A popular consortium blockchain platform is Hyperledger Fabric [2]}. Hyperledger Fabric represents as a consortium blockchain platform that was founded by the Linux Foundation in 2015. Similar to other blockchain technologies, Hyperledger Fabric has a ledger, uses smart contracts called chaincode, and coordinates participants in transaction organization. However, the concept of managing network access is different. Rather than an open permission-less system that enables the participation of all members in the network, the members of a Hyperledger Fabric network must be trusted by a membership service provider. Fabric takes a novel architectural approach and revamps the way blockchains cope with nondeterminism, resource exhaustion, and performance attacks. Fabric can also create channels, which enable a group of participants to establish a separate ledger of transactions. To achieve consensus in the network, Fabric uses Practical Byzantine Fault Tolerance (PBFT) which is well suitable for enterprise consortiums where members are partially trusted.

